300 EARTHS PROPER. 



97-36 



Let us consider it as a compound of three inte- 

 grant particles of silicate of alumina and one in- 

 tegrant particle of silicate of lime, together with 

 2-J atoms of water ; and let us calculate its com- 

 position according to that opinion. 



(1.) 2-25 : 2 : : 31-36 : 27'875 = silica united to alumina. 

 (2.) 3-5 : 2 : : 15-4 : 8-8 = silica united to lime. 



Now, 27-875 + 8-8 = 36-675, which is less than 

 the silica found in the mineral by 0*175 grain. 



The silica united to the lime is ith of the 

 whole. Now, iths of 0-175 = 0-132, which must 

 be added to the 27-875, in order to have the si- 

 lica actually united to the alumina in the mine- 

 ral ; this makes 28-007. And 



23395 28-007 : 31-36 : : 2 : 2-2395 = atomic weight of alumina. 



10. NATROLITE. 



This mineral, which corresponds with the meso- 

 type of Brooke, was analyzed with great care by 

 Gehlen and Fuchs. They found its composition, 

 from a mean of many experiments, as follows : 



